Sample records for kev range
from WorldWideScience.org

Sample records 1 - 2 shown.



1

Resolução lamelar num novo microscópio eletrônico de varredura/ Lamellar resolution in a new scanning electron microscope

Kestenbach, Hans-Jürgen; Nocite, Nádia C. P. S.; Gregório F°, Rinaldo; Loos, Joachim; Petermann, Jürgen
1997-03-01

Resumo em português RESUMO: Trabalhando com elétrons de baixa energia (na faixa de 1keV), o novo microscópio eletrônico de varredura dispensa a etapa de metalização e permite a observação direta da estrutura lamelar de polímeros semicristalinos, sem a necessidade de preparação de amostras. São apresentados exemplos da morfologia lamelar do PVDF em função das condições de processamento e da temperatura de cristalização, em filmes contendo as fases a, b e g. Um outro exemplo r (mais) evela o crescimento inicial da camada transcristalina que se formou ao longo de uma fibra de polietileno de ultra-alto peso molecular embutida em matriz de polietileno de alta densidade. Resumo em inglês ABSTRACT: Working with low energy electrons (in the range of 1keV), the new scanning electron microscope permits the lamellar (supermolecular) structure of semicrystalline polymers to be observed directly without the need of specimen coating or of any other sample preparation technique. Microscope performance is demonstrated by several examples of high resolution micrographs which show spherulitic, lamellar and fibrilar morphologies developed by the a, b and g phases of P (mais) VDF as a function of processing conditions and crystallization temperature. Another example reveals the early stages of transcrystalline layer formation in HDPE reinforced by UHMWPE fibers.

Scientific Electronic Library Online (Portuguese)

2

Excitação eletrônica das moléculas de metacrilato de metila e estireno na região do ultravioleta de vácuo/ Electronic excitation of the methyl methacrylate and styrene molecules in the vuv range

Rocco, M. L. M.; Souza, G. G. B. de; Lopes, M. C. A.; Lucas, C. A.
1998-02-01

Resumo em inglês Angle-resolved electron energy-loss spectra have been measured for the methyl methacrylate (MMA) and styrene molecules in the 0 - 50 eV energy range. The spectra have been obtained at 1 keV incident energy, with an energy resolution of 0.8 eV and covering an angular range of 2.0 to 7.0 degrees. Within our knowledge, this is the first gas-phase excitation spectrum for MMA and styrene in this energy range. The spectra of MMA at small scattering angles are dominated by an in (mais) tense peak at 6.7 eV followed by a broad band centered at about 16 eV. In the case of styrene, six bands can be observed in the spectra. Based on the angular behaviour of the excitation spectra of these molecules, the low-lying peaks observed are considered to be associated predominantly with dipole-allowed processes. In both cases, new bands can be observed for excitation energies greater than 20 eV. This could be associated with dipole-forbidden transitions to shake-up and doubly-excited states.

Scientific Electronic Library Online (Portuguese)